Throttling valve for compressed air or the like and its application to an airjet loom

ABSTRACT

A throttling valve (11) in particular for an airjet loom includes an electric drive (27) for two valve components (17, 19) subtending a throttling gap (25), the drive including motor displaceable in predetermined positions by means of a control and/or regulation unit for setting throtting gaps (25) of predetermined sizes.

BACKGROUND OF THE INVENTION Field of the Invention

The invention concerns a throttling valve for compressed air or the likeand comprising a first valve component and a second valve componentwhich together subtend an adjustable throttling gap, further an electricdrive to displace at least one of the valve components for the purposeof adjusting the size of the throttling gap.

Electromagnetically driven throttling valves are already known, whichcomprise an armature fitted at its end with a plunger subtending athrottling gap together with a stationary component. The plunger-fittedarmature can be displaced against a spring force by means of acurrent-fed coil. As a rule the spring biases the armature toward theclosed position. The plunger position is controlled by changing thecurrent in the coil. Thereupon the plunger assumes a position whereinthe magnetic force and the spring force are balanced.

As regards such throttling valves, the plunger position and hence infact the adjusted magnitude of the throttling gap depends on thetolerances for the spring constants and the tolerances affecting themagnetic drive. Most of the time comparatively complex control of theapplied current is also required in order that a constant force beapplied to the armature by means of a constant current into the coilregardless of coil temperature.

In such throttling valves, furthermore, the applied feed pressure of thecompressed air and the flow of the compressed air through the throttlingvalve will affect the plunger position. This feature is especiallydisadvantageous when the feed pressure and/or the magnitude of thethrottling aperture are changing.

Moreover such throttling valves evince hysteresis, and as a result theprecise plunger position is determined not only by the coil current butalso by the plunger's direction of motion.

Again the plunger position of such throttling valves will be affected byvibrations. Therefore such throttling valves are poorly suited for usein looms because looms generate vibrations by the beat motion of thereed and/or by displacements of the weaving frame.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to create a throttling valve of theinitially cited species making it possible to accurately setpredetermined throttling gaps and such that the valve isvibration-insensitive.

This problem is solved by the electric drive comprising a motordisplaceable by a control and/or regulation unit into predeterminedpositions in order to set throttling gaps of predetermined sizes.

In such a throttling valve, throttling gaps may be set precisely andthen may be kept accurately in place even if the throttling valve ismounted in a vibration-generating loom. The size of the adjustedthrottling-gap furthermore is insensitive to changes in the feedpressure of the compressed air and/or into the flow of compressed air.As a result the magnitude of the throttle aperture and thus the degreeof throttling can be set precisely.

In a preferred embodiment of the invention, the electric drive includesa stepping motor. The desired sizes of the throttling gap can beobtained very accurately using such a stepping motor.

Where an especially fine control of the throttling-gap sizes is desired,another embodiment of the invention provides that a reducing gear bemounted between the motor and the valve component it displaces. As aresult and in particular when using a stepping motor, thedesign-determined angular motor motions between the individual steps canbe reduced to comparatively small adjustment displacements of the valvecomponent(s). Another advantageous embodiment provides a helicoidal gearset between the plunger and the motor. This helicoidal gear set offersthe advantage that it directly converts the motor rotation intotranslation.

In a further embodiment of the invention, the two valve components are aplunger and an essentially cylindrical valve seat which are mutuallyaxially displaceable to adjust the throttling gap.

In yet another embodiment of the invention, the two valve components arefitted with seals that can be moved so they touch each other. Thisfeature allows one to transfer the throttling valve into a shutoffposition.

In still another embodiment of the invention, the throttling valve isused in an airjet loom and precedes a main blowing nozzle connected to asource of compressed air by at least one main valve feedinghigh-pressure compressed air to the main blowing nozzle or by throttlingvalve feeding compressed air of lower pressure to the main blowingnozzle.

Airjet looms comprise one or more main blowing nozzles each insertingone filling thread into a shed. During filling insertion, these mainblowing nozzles are loaded with high-pressure compressed air, forinstance between 2 and 7 bars. Moreover it is known to load the mainblowing nozzle precisely when it is not inserting a filling withcompressed air of lower pressure, for instance 0.02 to 1 bar. Thepurpose of this lower pressure is to prevent the filling thread fromdropping out of the main blowing nozzle during the time interval inwhich this main blowing nozzle is not inserting a filing. For thatpurpose a manually adjustable pressure reducer is installed, in additionto a first line containing a main valve, in a second line leading to themain blowing nozzle(s) and issuing from the same source of compressedair. The loom operator must manually adjust the lower pressure in suchmanner that on one hand the filling shall not drop out of the mainblowing nozzle during weaving while on the other hand this filling shallnot fray and be destroyed during loom shutdown for instance whenremedying a broken filling thread or the like. For this reason the lowerpressure also must be provided in such manner that during prolongedapplication of the low-pressure compressed air to the filling in themain blowing nozzle, said filling shall not fray and be destroyed.Setting a lower-pressure value that meets both conditions is exceedinglydifficult. Most of the time the adjusted lower pressure will be too lowto reliably keep the filling in the main blowing nozzle during weaving,while on the other hand will be so high that this filling will fray andbe destroyed during loom shutdown.

It is further known to install a second feed line with a second pressurereducer parallel to the feed line with the pressure reducer. In thatcase one of the pressure reducers is set to a lower pressure reliablypreventing the filling from dropping out of the main blowing nozzleduring weaving, the other pressure reducer being set to a lower pressurethat will not fray or destroy the filling present in the main blowingnozzle during loom shutdown. To meet these functions, shutoff valvesalso must be mounted in the particular feed lines to allow shutting themoff as needed. Additionally yet, check valves must be installed in eachfeed line to prevent high-pressure compressed air from being blown intothese feed lines when the main valve is open. Such a design alreadyentails substantial complexity for a main blowing nozzle alone andrequires much space. When a loom comprises several main blowing nozzles,this design becomes impractical.

The above problems are easily solved by the throttling valve of theinvention. Throttling gaps of predetermined size optimally matching theparticular operating conditions can be implemented by means of thecontrol and/or regulating unit. A throttling-gap size may be set whichshall in turn set a pressure reliably causing the filling to be held inthe main blowing nozzle during weaving. A further throttling gap ofpredetermined size may be adjusted and thereby a lower pressure may bepredetermined which, in the case of loom shutdown, allows reliablyholding the filling in the main blowing nozzle without however frayingor destroying it. It is feasible moreover to set a further predeterminedthrottling-gap size in turn setting a pressure level for instancebetween those of the two above cited pressures and allowing one,following filling rupture or the like, to suck a filling into the mainblowing nozzle. Lastly the throttling valve also can be moved into ashutoff position.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention are elucidated in thefollowing description of the embodiments shown in the drawings, where.

FIG. 1 is a schematic axial section of a throttling valve with itsassociated drive,

FIG. 2 is a detail F2 of FIG. 1 shown on a larger scale,

FIG. 3 is a section along line III--III of FIG. 2,

FIG. 4 is a section corresponding to FIG. 2 with the position of thevalve components different from that of FIG. 2,

FIG. 5 is a section corresponding to FIGS. 2 and 4 with the valvecomponents in still another position,

FIG. 6 is a graph showing the throttling by the valve of FIGS. 1 through5 as a function of the valve-component positions,

FIGS. 7 through 9 show valve components of another embodiment of athrottling valve in various positions of the valve components, and

FIG. 10 is a functional diagram for the compressed-air feed to two mainblowing nozzles of an airjet loom fitted with the throttling valves ofthe invention.

DETAILED DESCRIPTION

The throttling valve 11 shown in FIG. 1 contains two valve components,namely a stationary valve seat 17 having a cylindrical inside surface 18and an adjustable plunger 19 having a conical segment 20 and anadjoining cylindrical segment 33. The conicity of the conical segment 20is between 3 and 30° and preferably it is 5°. The diameter of thecylindrical plunger segment 33 matches the cylindrical inside diameter18 of the valve seat 17 in such manner that in the position shown inFIG. 4, the cylindrical segment 33 shall be displaceable with littleplay within the inside surface 18 of the valve seat. Moreover the valveseat 17 is fitted with an annular clearance 34 concentric to said seat'saxis and present on the end surface facing the plunger 19.

The throttling valve 11 comprises a housing 21 fitted with a firstborehole 22 communicating in a manner not shown in further detail with acompressed-air feed device. A second borehole 23 runs transversely tothe first borehole 22 and communicates with it and receives the plunger19. The valve seat 17 is located in the region where the boreholes 22and 23 are connected to each other. Said valve seat 17 is pressed intothe borehole 23. However any other affixation may be used, for instancebonding. The plunger 19 is axially displaceable into the valve seat 17and as a result a throttling gap 25 shown in FIG. 3 is subtended betweenthe inside cylindrical surface 18 of the valve seat and the conicalsegment 20 of the plunger 19. A third borehole 24 is configured in suchmanner transversely to the borehole 23 that the valve seat 17 is locatedbetween the borehole 22 and the borehole 24.

The compressed air arriving from a compressed-air source is fed from thefirst borehole 22 through the throttling gap 25, subtended between thecylindrical inside surface 18 of the valve seat 17 and the conicalsegment 20 of the plunger 19, and then to the third borehole 24.Throttling takes place as the compressed air passes through thethrottling gap 25. The compressed air arriving from the compressed-airsource and flowing through the restricted throttling gap 25 therefore isthrottled to a lower pressure and thereupon it is guided at that lowerpressure through the third borehole 24 toward an air consuming means,for instance a loom main blowing-nozzle. In its zone guided within theborehole 23, the plunger 19 is fitted with an annular seal 26 to preventcompressed air from escaping out of the borehole 23.

The plunger 19 can be moved by a drive 27 actuated by a control and/orregulating unit. The drive 27 contains a stepping motor having a rotor28 meshing by a helicoidal inside thread 28a with an outer helicoidalthread 28b of a plunger rod 29. The plunger rod 29 is fitted with alongitudinal groove 38 engaged by a pin 39 to prevent the plunger rod 29from rotating. The stepping-motor rotor 28 is axially fixed in thestepping-motor housing 35 and as a result rotations by the rotor 29 areconverted into axial displacements of the plunger rod 28 and hence ofplunger 19. The stepping-motor housing 35 is affixed by screws 30 on thehousing 21 of the throttling valve 11.

The design of the stepping motor and of the helicoidal gear set betweenthe rotor 28 and the plunger rod 29 is such that one rotational step ofthe step motor is reduced into an axial displacement of about 0.01 mm to0.05 mm, for instance 0.03 mm. The angular displacement of one step ofthe stepping motor as well as the pitch of the rotor 28 and of thethread of the plunger rod 29 are designed commensurately. The rotationof the rotor 28 entails displacing the plunger 19 relative to the valveseat and as a result the throttling aperture 25 will have been set. Thedrive allows displacing the plunger relative to the valve seats in stepsof hundredths of a mm.

The throttling valve 11 is displaceable into a shutoff position in orderto fully shut off the flow of compressed air from the borehole 22 to theborehole 24. The plunger 19 is fitted with an annular seal 31 placed inan annular groove 34 at the proximal end of the plunger and cooperatingwith a radial surface 40 of the annular groove 34 as shown in FIG. 5.The annular seal 31 is freely displaceable inside the annular groove 34of the valve seat 17 until the above sealing effect takes place. In theshutoff position, a rigid annular shoulder 36 of the plunger restsagainst the rigid end surface 32 of the valve seat 17. As elucidatedbelow, this position is the spatially fixed reference position. Asealing ring 37 is additionally provided between the valve seat 17 andthe borehole 23.

The annular seal 31 already will cooperate with the radial surface 40before the annular shoulder 36 of the plunger 19 comes to rest againstthe end surface 32 of the valve seat. The outside diameter of theannular seal 31 is larger than the axial depth of the annular groove 34.The elasticity of the annular seal 31 allows displacing the plunger 19between the position wherein the annular seal 31 already rests againstthe radial surface and the position in which the annular shoulder 36 ofthe plunger 19 rests against the end surface 32 of the valve seat 17.

FIG. 6 illustrates the flow Q of compressed air in relation to theposition P of the plunger 19 of the throttling valve 11. This functionis the result of the shapes of the plunger 19 and of the valve seat 17,in particular of the diameter of the inside surface 18 of the valve seat17 as well as of the diameter of the proximal cylindrical segment 33 ofthe plunger 19 and the position of the annular groove 34, of theconicity of the distal plunger segment 20 and the axial length A shownin FIG. 2 between the annular shoulder 36 and the conical segment 20 ofthe plunger 19. When in the position P₀, the plunger 19 is in theposition shown in FIG. 5. The throttling valve 11 is shut off, and theflow is zero. Then the plunger 19 moves in several steps in thedirection P as shown in FIGS. 5, 4 and 2. Beginning with the position P₁where the annular seal 31 detaches from the cylindrical surface 40 ofthe annular groove 34, a slight flow of air Q passes through thethrottling valve 11, namely a so-called leakage flow determined by theplay between the inside surface 18 of the valve seat 17 and thecylindrical segment 33 of the plunger 19 as well as by the axial lengthover which the cylindrical surface 18 and the cylindrical segment 33 ofthe plunger 19 are still cooperating, further by the distance betweenthe annular seal 31 and the annular groove 34. Because of the elasticdeformability of the annular seal 31, the position P₁ is not uniquelydetermined. The leakage flow however being minute, this indeterminacyentails no particular drawback.

Thereupon the plunger 19 moves on in several steps in the direction Pand arrives at the position P₂ shown in FIG. 4. The cylindrical segment33 of the plunger 19 has arrived at the end of the cylindrical insidesurface 18 of the valve seat 17. If the position deviates further fromthis position P₂, the flow Q through the throttling valve 11 will risemore markedly because the inside surface 18 of the valve seat 17henceforth cooperates with the conical segment 20 of the plunger 19,whereby the cross-section of the throttling gap 25 is enlarged andthrottling is lowered, that is, the compressed air is throttled less.Thereafter the plunger 19 arrives at the positions P₃ and P₄corresponding to FIGS. 2 and 1.

The range between the positions P₂ and P₄ of the plunger 19 of thethrottling valve 11 is ideally suited for setting the flow Qreproducibly and very accurately. The plunger 19 and the valve seat 17must be manufactured with correspondingly tight tolerances.

If the design is such that the plunger 19 requires for instance 100steps of a stepping motor of a drive 27 between its positions P₀ and P₄,then this plunger 19 can be set into a correspondingly large number ofpositions with throttling gaps of different sizes.

The position of the plunger 19 is determined by a control and/orregulating unit for the stepping motor. The control and/or regulatingunit is connected to a voltage source and feeds positive or negativevoltage pulses applied to two or more terminals of the stepping motor.

In order to calibrate the drive 27 of the throttling valve, the steppingmotor is fed with an appropriate number of pulses from the controland/or regulating unit so that, independently of its initial position,the plunger can be moved opposite the direction P toward the positionshown in FIG. 5, wherein the rigid annular shoulder 36 of the plunger 19rests against the rigid end surface 32 of the valve seat 17. After theplunger 19 has reached this position, further pulses of the samepolarity no longer shall rotate the rotor 28 into the heretoforedirection and accordingly will not move the plunger 19 any longer in thedirection P. The plunger 19 then is located in the spatially fixedreference position P₀.

Thereupon, by predetermining the number of pulses to be fed to thestepping motor, the plunger 19 is displaced in precisely defined axialmanner in the direction P and as a result the position of the plunger 19and thereby the throttling level are determined as a function of thedistance from the reference position P₀. The position of the plunger 19no longer depends on the pressure of the reduced-pressure source, on theair impedance of the particular elements and/or on the flow ofcompressed air. Again vibrations will be without effect on the positionof the plunger 19 and as a result the throttling valve 11 isvibration-insensitive. The individual positions of the plunger 19 can bepredetermined very accurately by means of the control and/or regulatingunit in relation to the reference position P₀ and therefore throttlingcan be predetermined very accurately too.

Moreover, play in the helicoidal gear set between the rotor 28 and theplunger rod 29 is also very easily compensated. For that purpose theparticular required position of the plunger 19 may be entered only fromone direction. If the plunger 19 must be moved opposite this directioninto a new position P, it shall be displaced by a few steps past thisdesired position P and then it shall be moved back into the desiredposition in the specified direction of displacement. As a result play ofthe helicoidal gear set will be reliably without effect on the desiredposition of the plunger 19.

In a practical embodiment, the feed pressure of the compressed air maybe between 2 and 7 bars and is regulated by a pressure regulator to apressure up to about 1,000 mbars. The pressure then extant at theborehole 22 can be throttled by the throttling valve of the invention inthe manner discussed above. The diameter of the plunger 19 in the regionof its cylindrical segment 33 and the diameter of the cylindrical insidesurface 18 of the valve seat 17 are approximately 3 to 4 mm. Theconicity of the segment 20 of the plunger 19 is 5°. The relative motionof the plunger 19 and the valve seat 17 is about 4 to 7 mm. Such athrottling valve allows implementing this axial displacement forinstance in 100 steps and illustratively the adjustment of throttlingmay be carried out in 10 mbar steps.

In an embodiment variation of the invention, the plunger 19 isstationary whereas the valve seat 17 is driven by a drive preferablyalso containing a stepping motor. In a further variation, both theplunger 19 and the valve seat 17 are fitted each with their own drive inorder to be able to carry out relative motions.

The embodiment shown in FIGS. 7 through 9 differs from that alreadydescribed in relation to FIGS. 1 through 5 only by the shape of theinside surface 18 of the valve seat 17 and by the shape of the plunger19. In this latter embodiment, the valve seat 17 is fitted with aconical inside surface 18 associated with a conical segment 20 of theplunger 19 adjoined by an annular seal 31 which, in the shutoff position(FIG. 9), will rest against the end surface 32 of the valve seat 17. Aconical throttling gap 25 between the valve seat 17 and the plunger 19is present in the embodiment of FIGS. 7 through 9.

The throttling valve 11 elucidated in relation to FIGS. 1 through 9 isideally suited for an airjet loom and is mounted therein as shown by thepneumatic functional diagram of FIG. 10.

FIG. 10 illustratively shows two main blowing nozzles 1, 2 of an airjetloom which are driven in predetermined sequences and then each willinsert a filling into a shed wherein further filling transportation issupported in known manner by relaying nozzles.

Each of the main blowing nozzles 1, 2 is connected by a first branch 4to a compressed-air source 13. This first branch 4 feeds high-pressurecompressed air for instance between 2 and 7 bars to the main blowingnozzles 1, 2 for purposes of filling insertion. A pressure regulator 6,a pressure accumulator 7 and a main valve 8 are mounted between thecompressed-air source 13 and each of the main blowing nozzles 1, 2. Thepressure regulators 6 are adjustable. The main valve 8 is a magneticvalve and is opened by a control unit 16 to insert a filling andthereafter is closed again.

Each of the main blowing nozzles 1, 2 is connected through a furtherbranch 5 to the compressed-air source 13 to feed low-pressure compressedair to the main blowing nozzles 1, 2. These two branches 5 comprise acommon pressure regulator 9, one throttling valve 11 each of the designdescribed in FIGS. 1 through 9, and one check valve 10 precluding thepressure, when released by the main valve 8, from entering thesebranches 5. The lines 14 of the branches 4 and the lines 12 of thebranches 5 are combined by the main blowing nozzles 1, 2 into one line15 in each case.

The control unit 16 allows adjusting the throttling valve 11 todifferent throttling gaps and hence to different, lower pressures atwhich the compressed air will flow toward the main blowing nozzles 1, 2.Basically the lower pressure is matched to the material of the fillingand as a result, obviously when different fillings of differentmaterials are inserted from the individual main blowing nozzles,correspondingly different low-pressure values will be set by the controlunit 16 at the main blowing nozzles 1, 2. The throttling valve 11 isadjusted in such manner by the control unit 16 that during weavingwithin the filling pauses, that is when precisely one of the two mainblowing nozzles 1 or 2 is not inserting a filling, these main blowingnozzles 1 or 2 shall be supplied with compressed air of lower pressurewhich however is high enough to reliably retain the particular fillingin the main blowing nozzle.Experience shows that the danger of thefilling dropping out of the main blowing nozzle 1 or 2 will be greatestwhen the filling is being cut and accordingly the control unit 16 mayadjust the throttling valve 11 so that, during such a time interval,compressed air of higher pressure shall be supplied, the pressure of thecompressed air thereafter being reduced by adjusting the throttlingvalve. If, depending on the weaving pattern, one of the fillings is notbeing inserted for some significant time, the control unit 16 may adjustby means of the throttling valve 11 a lower pressure for said timeinterval to prevent fraying. This pressure then will be raised again intimely manner before the next insertion of this filling. The controlunit 16 will set the throttling valve to a further reduced pressurelevel in the case of loom shutdown, for instance when remedying threadrupture. The pressure level of the compressed air then being blown intothe main blowing nozzles 1, 2 is determined in such manner that theparticular fillings shall be reliably gripped while nevertheless beingfraying-free and intact even upon prolonged exposure to this compressedair. Moreover the control unit 16 sets the throttling valve 11 to apressure allowing guiding and sucking-in a filling at the intake of themain blowing nozzle 1 or 2. Such a pressure may be lower than thatapplied to the main blowing nozzles 1, 2 during weaving to hold thefilling, but it will be larger than the pressure applied to the mainblowing nozzles 1, 2 during interruption of operation. Furthermore thecontrol unit 16 is able to fully shut off the throttling valve 11 andthis feature is advantageous in some operational conditions. Also, insome cases, the check valve 10 may be fully eliminated.

In an embodiment variation, a pressure transducer 16a in lines 12 beyondthe respective throttling valves 11, may be connected to thecontrol-loop fitted control unit 16. As a result, it is possible tocontrol and precisely maintain the desired pressure using the systemconstituting a control and regulating unit 16. In such a design thepressure regulator 9 ahead of the throttling valves 11 may be dropped.

The invention is not restricted to the shown and discussed illustrativeembodiments used solely for elucidation. Equivalent designs, inparticular regarding the drive 27 and/or the valve elements 17, 19, arewithin the realm of the expert.

Illustratively mutually rotatable valve components subtending athrottling gap also may be used. Two telescoping cylindrical mutuallyrotatable valve components may be used which are fitted withcross-boreholes made to coincide more or less by such a rotation,whereby a commensurately larger or smaller throttling gap and also ashutoff position may be set. In such a case one or both valve componentsare rotated by the drive containing a stepping motor and preferably alsoa reduction gear.

The main valve 8 and the throttling valve 11 shown in FIG. 10 may bemounted in practice in a common housing which where appropriate alsocontains the check valve 10 if at all present.

We claim:
 1. A throttling valve for controlling flow of compressedgaseous fluid such as air, comprising:first and second relativelymovable valve components, the relative positions of which define anadjustable throttling gap between the components; an electric driveconnected to at least one of the valve components to move one valvecomponent relative to the other to establish the size of a throttlinggap between said components; said electric drive comprising a steppertype motor displaceable by a control unit into predetermined positions,each position corresponding to a predetermined size of said throttlinggap; a control unit connected to the electric drive motor forselectively driving the motor into select ones of said predeterminedpositions and into a spatially fixed reference end position; said valvecomponents including a plunger and a rigid valve seat; said plungerhaving a distal frusto-conical profile extending over a majority lengthof the plunger and an adjacent proximal cylindrical profile forcooperating with said valve seat; said plunger further including a rigidradial shoulder terminating the cylindrical profile opposite to thefrusto-conical profile, said shoulder being larger in diameter than saidvalve seat; said radial shoulder rigidly abutting said valve seat in theclosed position, said closed position with the shoulder rigidly abuttingsaid valve seat constituting said spatially fixed reference endposition; an airjet loom having at least one main filling blowingnozzle; a source of compressed air; and at least one main valve forregulating cyclic flow of compressed air to said main nozzle; saidthrottling valve controlling flow of compressed air from said source ofcompressed air to said at least one main nozzle when said valve isclosed; said throttling valve supplying compressed air from saidcompressed air source to said main blower nozzle at a lower pressurethan air supplied to the nozzle by said main control valve; said loomincluding a control unit programmable for different main nozzleoperating conditions connected to said motor for controlling the size ofthe throttling gap and thereby the flow of air to said main nozzle inaccordance with different desired main nozzle operating conditions; acompressed air supply line between said at least one throttling valveand at least one main nozzle, and an air pressure sensor in said airsupply lines; said pressure sensor providing a pressure signal to saidcontrol unit; said control unit programmed to process said air pressuresignal and to control the electric motor in response to a processed airpressure signal in accordance with said different desired main nozzleoperating conditions.
 2. A method of operating a throttling valve forcontrolling flow of compressed gaseous fluid such as air, wherein thethrottling valve includes first and second relatively movable valvecomponents, the relative positions of which define an adjustablethrottling gap between the components; an electric drive connected to atleast one of the valve components to move one valve component relativeto the other to establish the size of a throttling gap between saidcomponents; said electric drive comprising a stepper type motordisplaceable by a control unit into predetermined positions, eachposition corresponding to a predetermined size of said throttling gap;said control unit connected to the electric drive motor for selectivelydriving the motor into select ones of said predetermined positions andinto a spatially fixed reference end position; said valve componentsinclude a plunger and a rigid valve seat; said plunger having a distalfrusto-conical profile extending over a majority length of the plungerand an adjacent proximal cylindrical profile for cooperating with saidvalve seat; said plunger further including a rigid radial shoulderterminating the cylindrical profile opposite to the frusto-conicalprofile, said shoulder being larger in diameter than said valve seat;said radial shoulder rigidly abutting said valve seat in the closedposition, said closed position with the shoulder rigidly abutting saidvalve seat constituting said spatially fixed reference end position;comprisingadvancing said plunger by said stepper motor to causeengagement of said rigid radial shoulder with said rigid valve seat toestablish the position of said plunger at said reference end position;and than incrementally moving said rigid radial shoulder away from saidrigid valve seat by said stepper motor into selected ones of saidpredetermined positions to establish selected ones of said throttlinggap, whereby said reference end position enables establishment of saidthrottling gap as a function of the distance said plunger has moved awayfrom said reference position.
 3. The method as claimed in claim 2,wherein said valve components include at least one resilient sealingelement and a cooperating sealing surface that engage each other to sealthe components relative to each other when the valve is in the referenceend position, including moving said rigid radial shoulder fully to saidrigid valve seat without interference or effect by said sealing elementand sealing surface when advancing said plunger to establish saidreference end position.
 4. The method as claimed in claim 2, includingdriving the valve component connected to the drive motor through areducing gear disposed between the drive motor and the respective valvecomponent.
 5. The method according to claim 4, including using ahelicoidal gear set as the reducing gear between the drive motor and therespective valve component.
 6. The method as claimed in claim 2, whereinthe throttling valve is used in combination with an airjet loom havingat least one main filling blowing nozzle; a source of compressed air;and at least one main valve for regulating cyclic flow of compressed airto said main nozzle; comprising the additional steps of:controlling flowof compressed air from said source of compressed air to said at leastone main nozzle via said throttling valve when said main valve isclosed, including causing said throttling valve to supply suchcompressed air at a lower pressure than air supplied to the nozzle bysaid main valve.
 7. The method as claimed in claim 5, wherein the airjetloom includes a loom control unit programmable for different desiredmain nozzle operating conditions connected To said electric drive,comprising the additional step of controlling the throttling gap by saidloom control unit and therefore the flow of air to the main nozzle inaccordance with said desired main nozzle operating conditions.
 8. Themethod as claimed in claim 7, wherein the loom includes a compressed airsupply line between said throttling valve and the at least one mainnozzle and an air pressure sensor in said air supply line, comprisingthe additional steps of:providing air pressure signals from said airpressure sensor to said control unit; processing the air pressuresignals in the loom control unit to produce processed control signalsrelated to said different desired main nozzle operating conditions; andcontrolling the electric drive of the throttling valve in response tosaid processed control signals.